ECSS Paris 2023: OP-AP13
INTRODUCTION: Climbing performance relies heavily on body posture and weight distribution, with finger force application playing a critical role. Despite its importance, hand pressure has rarely been addressed in wearable sensor technologies due to limited space for sensor placement on the fingers, the delicate and complex nature of finger movements, and varying regulations regarding sporting gloves across disciplines. In our previous work (Kuo & Wu, 2025), a prototype smart sporting glove embedded with four thin-film force-sensitive resistor (FSR) sensors demonstrated the feasibility of automatic grip classification using convolutional neural network (CNN) models. METHODS: In the present study, the smart glove prototype was expanded to incorporate nine FSR sensors distributed across the hand to enable finer characterization of diverse gripping styles. Experiments were conducted with six male and female climbers across amateur, experienced, and professional levels. Hand pressure signals were collected during standardized gripping tasks and normalized prior to analysis. CNN-based models were trained to classify grip types, while repeated trials were used to assess fatigue-related changes in grip behavior. RESULTS: After signal normalization, consistent pressure patterns were observed for identical gripping motions across participants, supporting robust CNN-based grip classification. Fatigue effects were evident through progressive shifts in grip strategies and technique deterioration over repeated trials. Comparisons across skill levels revealed a negative correlation between climbing experience and signal noise associated with slipping. Amateur climbers exhibited higher finger force output and greater variability in pressure signals compared with experienced and professional climbers. CONCLUSION: The results suggest that excessive finger force in amateur climbers is linked to suboptimal posture and reduced reliance on whole-body balance strategies, contributing to higher fatigue rates. This study demonstrates the potential of a multidimensional, wearable sensing approach for objective performance and fatigue analysis in climbing. Future work will focus on expanding the dataset to establish generalized signal models of climbing ability across diverse anthropometric profiles, thereby improving the broader applicability of the proposed system.
Read CV Kuan Chen WuECSS Paris 2023: OP-AP13
INTRODUCTION: HYROX is a global fitness competition combining running with standardized functional tasks [1]. Although sled loads are fixed, athletes report differences in sled push and pull resistance within and between events, often attributed to turf conditions. This variability raises concerns about performance fairness. Existing friction assessment methods are not suited for field use due to limited portability [2], complex setup, or inability to quantify both static and dynamic friction. The aim of this study was to develop and test a field-deployable portable system for pre-race evaluation of turf friction in fitness competitions. METHODS: A motorized pulling device was built to move a loaded sled at a constant velocity, while recording pulling force at 50 Hz using an inline Bluetooth force sensor. The system performed automatic self-calibration at startup. For each trial, the user set the pulling speed and distance. The system recorded and analyzed force signal to identify the onset and steady-movement. Static coefficient of friction was calculated from the peak force before motion, and dynamic coefficient from the mean force during constant velocity, assuming equilibrium conditions. Preliminary testing was conducted in a HYROX-affiliated gym in Stockholm. Two sled lanes were evaluated: synthetic grass-like turf (T1) and cloth-like turf (T2). Loads from 49 to 169 kg (15 kg increments) were tested with two repeated trials. An additional wet condition (T2-W) was tested to simulate moisture accumulation during events. The mean static and dynamic coefficients of friction of repeated trials were calculated and compared RESULTS: The system was transportable in a standard backpack. Setup time was under five minutes, with no reset required between trials. Repeated trials showed high repeatability and measured coefficients were within ranges reported in the literature [2]. Under dry conditions, T1 showed higher static and dynamic friction than T2 at all loads. Mean dynamic friction across loads was 0.34 for T1 and 0.28 for T2. Differences increased with load: static friction differed by 13–18% and dynamic friction by 12–15% from the lightest to the heaviest sled. In the wet condition, T2-W had higher static and dynamic friction compared with dry T2, where effect appears to decrease with load. T2-W showed greater variability, likely due to uneven water distribution. CONCLUSION: Preliminary data indicates that changes in material, differences between lanes or venues, as well as moisture changes during events affects sled resistance and can influence performance outcomes. Pre-event friction assessment with a portable device is viable and can identify inconsistencies between surfaces and support improved competition standardization. Further testing will include a larger sample of repeated trials on official competition turf in collaboration with HYROX, and evaluation of additional conditions such as chalk, temperature, and floor attachment. [1] Brandt et al. (2025) [2] Andre et al. (2013)
Read CV Mariah SabioniECSS Paris 2023: OP-AP13
INTRODUCTION Previous empirical research generally indicates that the implementation of Video Assist referee (VAR) system can improve accuracy in reviewable incidents and may reduce certain forms of referee bias, although this may be accompanied by interruptions and altered match experience (1,2). The present study addresses referees’ disciplinary decision-making by estimating whether VAR implementation in the English Premier Leage (EPL) is associated with changes in three different outcomes: yellow cards, red cards, and penalties awarded per match. Red cards and penalties are directly reviewable under the VAR protocol, whereas yellow cards are not; examining all three outcomes therefore allows assessment of both direct VAR‑related effects and potential indirect behavioural or strategic disciplinary decision-making in refereeing practice. METHODS To estimate the causal effect of VAR on disciplinary outcomes in EPL, this study employs a Difference-in-Differences (DiD) design (3) rather than a traditional pre-post analysis. By comparing the change in outcomes in the EPL with the trends observed in the Championship, the DiD allows us to "differentiate away" time-invariant differences between the leagues and control for common time trends, for example changes in refereeing practices. With match-level data from the 18/19 season (without-VAR) and the 23/24 season (with-VAR), and the English Championship as a control group, a DiD analysis was completed to estimate the contributing effect of VAR’s impact on: yellow cards, red cards, and penalties awarded per match. RESULTS The findings indicate a statistically significant increase in all three outcomes in the Premier League following the introduction of VAR, compared to the Championship. The estimated DiD effect for yellow cards is 0.37 per match (SE = 0.0277; 95% CI [0.3157, 0.4243]; p < 0.001). For red cards, the estimated effect is 0.07 per match (SE = 0.0036; 95% CI [0.0629, 0.0771]; p < 0.001). For penalties, the estimated DiD effect is 0.07 per match (SE = 0.0068; 95% CI [0.0566, 0.0834]; p < 0.001). CONCLUSION Red cards and penalties, show increases that may reflect improved identification of clear and obvious errors attributed to the implementation of VAR. Meanwhile, the increase in yellow cards, which are not reviewed by VAR, may reflect indirect disciplinary behavioral changes due to heightened surveillance. The DiD analysis provide robust evidence that the implementation of VAR in the EPL has had a significant impact on refereeing disciplinary decisions by more yellow and red cards handed out and more penalties been awarded. Future research should explore the long-term effects of VAR, such as how it influences the referees’ decision-making after an incorrect on field decision previously has been identified by VAR, and conduct comparative analyses across different leagues. 1. Scanlon et al., (2022), Soccer & Society. 2. Spitz et al., (2021), Journal of Sport Sciences. 3. Callaway, & Sant’Anna, (2021), Journal of Econometrics. 4. Angrist & Pischke, (2009), Princeton University Press.
Read CV Bjoern Tore JohansenECSS Paris 2023: OP-AP13